The amount of energy required to move an electron from one energy level to the next higher one is known as

The amount of energy required to move an electron from one energy level to the next higher one is known as quantum.
It refers to the smallest amount of energy that is needed to do anything, so it can be applied here as well when it comes to moving electrons between levels. It belongs to quantum physics, which deals with quantum theory, which studies molecular, atomic, and sub-atomic levels. 

Most likely a is the answer - because  you generate   38 atp's but also consume an atp.   each atp gives approx. less than 4 kcal so probably a is the closest answer.